Various embodiments are described herein for a system and a method for identifying a region of interest in tissue using mass spectrometry. An agent administration component can be provided to administer an exogenous agent to the tissue. A sampling unit can also be provided to acquire a sample from the tissue. The sample can then be provided to a high sensitivity analysis platform, such as a mass analyzer, to analyze the sample and determine a distribution of the exogenous agent or a by-product of the exogenous agent within the tissue based on the analysis. The analysis platform can then identify the region of interest based on the distribution of the exogenous agent or the distribution of the by-product.